Document Type : Original Article
Authors
1 Students’ Research Committee, Nursing and Midwifery Faculty, Tabriz University of Medical Sciences, Tabriz, Iran
2 Midwifery Department, Tabriz University of Medical Sciences, Tabriz, Iran
3 Social Determinants of Health Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
4 4Department of Statistics and Epidemiology Faculty of Health Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
5 5Department of Obstetrics and Gynecology, Tabriz University of Medical Sciences, Tabriz, Iran
Abstract
Keywords
Endometriosis is a benign gynecologic disease (
Endometriosis has a complex and multifactorial etiology
(
Although no theory can cover all the manifestations of
this disease, the retrograde menstruation is widely accepted
to describe the dissemination of endometrial tissue to
the peritoneal cavity through open fallopian tubes during
menstruation (
It is hypothesized that sexual activity leading to orgasm during
menstruation may increase retrograde menstruation, seeding
endometrial tissue in other locations, and thus increasing
the risk of endometriosis. So far, few studies have examined
the relationship between sexual activity during menstruation
and endometriosis (
This case-control study, which was done in 2017, recruited women at reproductive age (20-50 years), with or without endometriosis. The participants in the case group were selected from women with endometriosis visiting Alzahra Hospital over the past two years, who had undergone laparoscopy and open surgery with a histological diagnosis of endometriosis. Participants in the control group were selected from the same age group of women visiting the same hospital for other reasons including vaginitis and an annual checkup. The absence of endometriosis in the control group was confirmed by a gynecologist colleague based on their signs and symptoms. The final selections were done based on our inclusion and exclusion criteria. The study inclusion criteria were: i. Age of 20-50 years, ii. Diagnosis of endometriosis by open surgery or laparoscopy and histologic diagnosis of endometriosis or the presence of endometrioma (case group), iii. Being married, iv. Being Iranian, v. Willingness to participate, vi. Absence of endometriosis (control group), vii. No history of tubectomy (control group), and viii. No history of infertility (control group).
The study exclusion criteria were: i. Being menopausal (amenorrhea for over a year), ii. Being suspected of endometriosis or endometrioma (control group), iii. Having endometriosis in the surgical site or involvement of remote organs, e.g. lungs or brain, iv. Having breast, ovarian, or endometrial cancer, v. Having polycystic ovarian syndrome (PCOS), vi. Having any other life-threatening disease, and vii. Suffering from chronic pelvic pain.
In this study, the sample size was determined according to the results of a pilot study on 150 participants and considering an odds ratio (odds of having sexual activity in the menstruation in the case group compared with the control group) to be about 1.8, was determined as n1=185 (case group), n2=370 (control group), and n=555 (total) (with the case-to-control ratio of 1:2).
The present study was confirmed by the Ethics Council of Tabriz University of Medical Sciences (ethics code: 5/ D1003687). Afterward, data collection was started in Alzahra Hospital, Tabriz, which is a referral Gynecology and Midwifery Hospital in Northwest of Iran. We reviewed pathological results in the medical files that were available at Alzahra Hospital and registered women patients with endometriosis, as confirmed by histological diagnosis through laparoscopy or open surgery, for our study. The addresses and phone numbers of all considering patients, who had been identified over the past two years, were extracted from their records. They were contacted by telephone, the research objectives and methods were briefly explained to them, the study inclusion and exclusion criteria were checked, and finally they were invited to participate in the study. For those who were willing to take part, questionnaires were filled in through the interview. For the patients’ comfort, the interviewer and the patients were of the same gender. After sampling was done in the case group, the members of the control group were selected through purposive sampling from those visiting the gynecology clinic of the same center for other issues, such as vaginitis or an annual visit, and did not have endometriosis, as diagnosed based on symptoms by a gynecologist colleague. Research objectives and methods were first explained to them. For those who were willing to participate, inclusion and exclusion criteria were checked, and in case they met the criteria, they were recruited and questionnaires were completed by the researcher through interviews. Informed consent forms were obtained from all participants, and those in both case and control groups were matched for age ± 2 years.
Data were collected by the researchers through interviews and using researcher-made questionnaires based on previous studies, highlighting sociodemographic and sexual activity characteristics. The sociodemographic characteristics questionnaire included questions on age; the level of education, employment, the level of income, smoking, alcohol use, the history of any diseases, allergies, and endometriosis in first-degree relatives (mother, sisters, and aunts). The sexual activity and reproductive and menstruation characteristics questionnaire included questions on vaginal or non-coital sexual activity (by touching other body parts by the person or her spouse to achieve sexual pleasure) and anal intercourse, leading to orgasm during menstruation, cycle length, cycle intervals, number of pregnancies, menarche age, age at first pregnancy, oral contraceptive pill (OCP) user, intrauterine device (IUD) user, dysmenorrhea, dyspareunia, and recurrent vaginitis. Content and face validity were used to confirm the validity of the questionnaires, they were given to 10 faculty members and corrections were applied based on their opinions.
Data were analyzed in SPSS 21 software. Sociodemographic and sexual activity characteristics during menstruation were described using descriptive statistics including frequency (percentage). Sociodemographic characteristics were compared between the two groups using chi-squared test, chi-squared test for trend, independent samples t test, and Fisher’s exact test. To determine the relationship between sexual activity during menstruation and endometriosis, chi-squared test was performed in the bivariate analysis. Conditional logistic regression was employed in the multivariate analysis to control confounding variables (level of education, level of income, occupation, cycle length, cycle interval, number of pregnancies, menarche age, age at first pregnancy, OCP user, IUD user, dysmenorrhea, dyspareunia and recurrent vaginitis). Because no woman in the control group reported a history of this disease in her first-degree relatives, the family history was not included in the multivariate regression as a confounding factor. In this analysis, the odds ratio and confidence interval was set at 95%, and P<0.05 was considered significant.
In this study, 185 women with endometriosis and 370
women without endometriosis were analyzed. The participants’
mean age was 35.21 years (SD: 7.09) in the case
group and 35.28 years (SD: 7.03) in the control group. The
two groups significantly were differed regarding the level
of education; the percentage of participants with academic
degrees in the case group was twice as high as those in the
control group (P<0.001). Moreover, 32 (17.3%) women of
the case group and 10 (2.7%) women of the control group
were employed, again indicating a significant difference between
the two groups (P<0.001). However, the two groups
were similar regarding the sufficiency of monthly income
(P=0.698). The two groups were compared in a history of
diseases such as diabetes, hypothyroidism, hypertension,
cardiovascular diseases, cerebrovascular diseases, seizures
and asthma, and did not show any significant differences
(P=0.860). The two groups were also similar regarding an
autoimmune disease history, e.g. rheumatoid arthritis, multiple
sclerosis, and lupus erythematosus (P=0.669). There
were 38 (20.5%) women in the case group and 47 (12.7%)
women in the control group with a history of allergies, indicating
a significant difference between the two groups
(P=0.016). Nevertheless, both groups were similar regarding
the type of allergies (seasonal, food, drug, or skin)
(P=0.946). In the case group 13 (7%) women reported a
history of endometriosis in their mothers and sisters, and 7
(3.8%) women reported this in their aunts, while no woman
in the control group reported a history of this disease in
her first-degree relatives, demonstrating a significant difference
between the groups (P<0.001). Only one woman in
the control group had a history of smoking, and no one in
either group had a history of alcohol use (
Comparison of sociodemographic characteristics in case and control groups
| Social-demographic characteristic | Case n=185 | Control n=370 | P value |
|---|---|---|---|
| Age (Y) | 35.21 (7.09)§ | 35.28 (7.03)§ | 0.909** |
| Education | <0.001‡ | ||
| Illiterate/Primary | 57 (30.8) | 129 (34.9) | |
| Guidance/High school | 37 (20.0) | 82 (22.2) | |
| Diploma | 39 (21.1) | 107 (28.9) | |
| Academic | 52 (28.1) | 52 (14.1) | |
| Occupation | <0.001* | ||
| Housewife | 153 (82.7) | 360 (97.3) | |
| Employed | 32 (17.3) | 10 (2.7) | |
| Job type | 1.000† | ||
| Doctor/University professor | 7 (21.9) | 2 (20.0) | |
| Employee | 21 (65.6) | 7 (70.0) | |
| Free | 4 (12.5) | 1 (10.0) | |
| Adequacy of monthly income | 0.698‡ | ||
| Weak | 42 (22.7) | 79 (21.4) | |
| Average | 102 (55.1) | 197 (53.2) | |
| Good/Very good | 41 (22.2) | 94 (25.4) | |
| Having a history of a disease | 24 (13.0) | 50 (13.5) | 0.860* |
| Having a history of autoimmune disease | 1 (0.5) | 4 (1.1) | 0.669† |
| Having a history of allergies | 38 (20.5) | 47 (12.7) | 0.016* |
| The history of first-degree relatives | <0.001† | ||
| Yes | 20 (10.8) | 0 | |
| No | 165 (89.2) | 370 (100.0) | |
Data are presented n (%). *; Chi-squared test, ‡; Chi-squared test for trend, †; Fisher’s exact test, §; Mean ±SD, and **; Independent samples t test. Only one woman in the control group had a history of smoking, and no one in either group had a history of alcohol use.
Regarding vaginal intercourse during menstruation, the
two groups were compared using multivariate logistic regression,
while controlling the effects of possible confounding
variables, such as the level of education, income, occupation,
cycle length, cycle interval, number of pregnancies,
menarche age, age at first pregnancy, OCP user, IUD user,
dysmenorrhea, dyspareunia and recurrent vaginitis. The results
showed that the risk of endometriosis approximately
was five times higher in those women who stated they had
vaginal intercourse during menstruation compared to those
who stated they did not [(P<0.001), odds ratio (OR) (95%
confidence interval (CI)=5.23 (2.16 to 12.66)]. Furthermore,
6 (20%) participants in the case group and 1 (3.6%)
participant in the control group reported that they always
had vaginal intercourse during menstruation, demonstrating
a significant difference between the groups (P<0.001).
Both groups were similar with regard to the days of vaginal
intercourse (first three days, second 3 days, all days of menstruation)
(P=0.111). Moreover, the risk of endometriosis
was approximately three times higher in those women who
stated they had non-coital sexual activity during menstruation
compared to those who stated they did not [(P=0.010),
OR (95% CI)=2.90 (1.28 to 6.55)]. In addition, 9 (23.7%)
participants in the case group and 6 (14.6%) participants in
the control group reported that they always had non-coital
sexual activity during menstruation, indicating no significant
difference between the two groups based on a chi-
squared test (P=0.141). Moreover, 2 (1.1%) participants
in the case group and 15 (4.1%) participants in the control
group stated that they have anal intercourse during menstruation,
but there was no significant difference between
the two groups [(P=0.130), OR (95% CI) = 0.08 (0.03 to
2.09)] (Tables
Comparison of sexual activity during menstruation and reproductive and menstruation characteristics in case and control groups based on bivariate test
| Sexual activity during menstruation and reproductive and menstruation characteristics | Case n=185 | Control n=370 | P value |
|---|---|---|---|
| Vaginal sex activity | 0.002* | ||
| Yes | 30 (16.2) | 28 (7.6) | |
| No | 155 (83.8) | 342 (92.4) | |
| Sexual activity without vaginal penetration | 0.003* | ||
| Yes | 38 (20.5) | 41 (11.1) | |
| No | 147 (79.5) | 329 (88.9) | |
| Anal sex activity | 0.075† | ||
| Yes | 2 (1.1) | 15 (4.1) | |
| No | 183 (98.9) | 355 (95.9) | |
| Age at menarche | <0.001* | ||
| ≤ 12 | 54 (29.2) | 64 (17.3) | |
| >12 | 131 (70.8) | 306 (82.7) | |
| Cycle interval | 0.012* | ||
| ≤ 28 | 109 (58.9) 176 (47.6) | ||
| > 28 | 76 (41.1) | 194 (52.4) | |
| Cycle length | <0.001* | ||
| ≤ 7 | 136 (73.5) | 357 (96.5) | |
| > 7 | 49 (26.5) | 13 (3.5) | |
| Pregnancy number | <0.001* | ||
| 0/1 | 102 (55.1) | 80 (21.6) | |
| ≥ 2 | 83 (44.9) 290 (78.4) | ||
| OCP user | 0.303* | ||
| Yes | 75 (40.5) | 167 (45.1) | |
| IUD user | 0.017* | ||
| Yes | 42 (22.7) | 120 (32.4) | |
| Age at first pregnancy | 0.037* | ||
| ≤ 20 | 43 (30.1) | 146 (40.0) | |
| > 20 | 100 (69.9) | 219 (60.0) | |
| Dysmenorrhea | <0.001* | ||
| Yes | 136 (73.5) | 43 (11.6) | |
| Dyspareunia | <0.001* | ||
| Yes | 82 (44.3) | 7 (1.9) | |
| Recurrent vaginitis | <0.001* | ||
| Yes | 50 (27.0) | 18 (4.9) | |
*; Chi-squared test and †; Fisher’s exact test.
Comparison of sexual activity during menstruation in case and control groups based on bivariate and multivariate logistic regression
| Variable | Unadjusted | Adjusted | ||
|---|---|---|---|---|
| P value | OR (CI 95%) | P value | OR (CI 95%) | |
| Vaginal sex activity | 0.002 | 2.36 (1.36 to 4.09) | <0.001 | 5.23 (2.16 to 12.66) |
| Sexual activity without vaginal penetration | 0.003 | 2.07(1.28 to 3.36) | 0.010 | 2.90 (1.28 to 6.55) |
| Anal sex activity | 0.075 | 0.25(0.05 to 1.14) | 0.130 | 0.08 (0.03 to 2.09) |
Conditional logistic regression was employed (P<0.1) in the multivariate analysis to control confounding variables: level of education, level of income, occupation, cycle length, cycle interval, pregnancy number, menarche age, age at first pregnancy, OCP user, IUD user, dysmenorrhea, dyspareunia, and recurrent vaginitis. CI; Confidence interval, OR; Odds ratio, OCP; Oral contraceptive pill, and IUD; Intrauterine device.
The present study is the first study in Iran, which examined the association between sexual activity during menstruation and endometriosis. Our results revealed that vaginal intercourse and non-coital sexual activity leading to orgasm during menstruation increase the risk of endometriosis.
The case and control groups were significantly different
regarding the level of education and occupation. Most recent
epidemiological studies on risk factors for endometriosis
have shown an increased incidence of the disease
among women of high socioeconomic and occupational
status (
There are few studies on the association between sexual
activity during menstruation and endometriosis. For
instance, Meaddough et al. (
Another study was conducted by Filer and Wu (
In this study, there was no significant difference between the groups in terms of having anal intercourse leading to orgasm during menstruation. However, due to the limited number (only two women in the control group), a complete conclusion is not possible.
In this study, an attempt was made to select women with and without endometriosis based on precise medical diagnosis. Furthermore, the most important and relevant factors with endometriosis were examined while controlling confounding variables.
In this study, validity was only confirmed through face and content validity qualitatively and the quantitative indices such as content validity index (CVI) and content validity ratio (CVR) weren’t calculated. Also, considering the criterion for the definite diagnosis of endometriosis is histologic diagnosis through laparoscopy or laparotomy, one of the other shortcoming of this study is that the control group wasn’t selected based on histologic diagnosis. Thus, future studies should be conducted on selected case and control participants from women, in whom the presence or absence of endometriosis is confirmed by laparoscopy or laparotomy.
Based on the results of the present study, vaginal intercourse or non-coital sexual activity leading to orgasm during menstruation increases the risk of endometriosis in women during reproductive age. This study has raised interesting issues and requires further investigation to better understand the mechanism of occurrence of endometriosis in such cases.
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